1. Technical Field
The present invention generally relates to an iris recognition system, a method thereof, and an encryption system, and more specifically, to an iris recognition system, a method thereof, and an encryption system having an image extractor for extracting a good image by using a mask from a plurality of images taken by a camera.
2. Background
Personal encryption or personal identification number which is widely used as a traditional method for identifying a person cannot satisfy requirements for stable and exact personal identification in an information society that gradually becomes more developed and ultramodern owing to plagiarism and a risk of loss, and also it can cause a lot of side effects in the entire society due to dysfunction. Particularly, the rapid development of the Internet environment and a sudden increase of E-commerce can predict that there would be tremendous physical and mental losses of persons and groups by only using past traditional personal authentication methods.
As an alternative for complementing demerits of the traditional personal identification methods, biometrics is spotlighted as the most stable and exact personal identification method. Biometrics is a method for identifying a person based on physical (biological) characteristics and behavioral characteristics of each person, and in this case, fingerprints, face, iris, and the lines of the palm may be included in the physical characteristics while signature and voices are classified as the behavioral characteristics. Such personal identification and security based on the personal characteristics cannot be delivered by theft or leakage with no risks of alterations or loss, thus it is possible to perfectly construct an audit function, for instance, a person who makes an infringement can be tracked down.
Especially, among various biometric methods, it is known that the iris of the eye is the most superior part to identify a person in terms of uniqueness, invariability, and stability. Moreover, since an incorrect recognition rate of the iris is very low, the iris is tending to be applied to certain fields that require high-level security.
The iris is fully formed before a baby becomes 3 years old after being born, and if is known that the iris is not changed through life unless special external wounds are inflicted. Also, iris patterns are more various than fingerprints and up to now, it is known as the most perfect personal identification method. Since image acquisition is available in noncontact way, user convenience is also very good, thus it is predicted that market potential would be very high.
Generally, in a method for recognizing a particular person by using the iris, fast detection for the pupil and the iris is essential for real-time iris recognition from an image signal produced by taking a picture of the eye part of a human being. An iris recognition system has a configuration like shown in FIG. 1. The iris recognition system comprises an image input device (10) for inputting a user's iris image, an iris image processor (100) for processing the inputted iris image, an iris image register (200) for registering iris images according to each user, and an iris DB (500) for storing the iris images, then comprises an iris pattern verifier (300) for deciding whether output of the iris image processor (100) and the iris stored in the iris DB (500) are consistent together when authentication is performed. Dotted line arrows of FIG. 1 show a flow that the iris is registered in the iris DB, and solid line arrows display a procedure of taking a picture of an iris of an authenticator and comparing the taken iris with the iris stored in the iris DB to authenticate the compared irises.
A first step of iris recognition is to select a good image among a plurality of images inputted from an image input device. The images inputted from the image input device are different in qualities according to brightness of lighting or spatial environment for image acquisition and a degree of a user's motion. Most of the current iris recognition system has improved a lot in quality deterioration caused by spatial environment, thanks to the development of image input device technology and the development of lighting technology. However, deterioration of image quality resulting from inexperience of the user should be handled by being examined in an inputting step.
If the user who is unfamiliar with iris recognition uses the image input device, it is not easy for the user to adjust a focal distance. As a result, an automatic focus input image device is mostly used for iris recognition, but this device takes the focus only. So, in order to obtain an image having a certain degree of contrast an image of more than a certain quality should be obtained by using a certain degree of a contrast value as a threshold value.
The prior method for obtaining a good image from a plurality of images taken by the image input device is to examine noise (motion blurring) caused by motion and resolution of iris images. The resolution examination is conducted by calculating contrast and a degree of change of light and shade for a certain range of regions around the edge of the pupil, while the method for examining the noise caused by the user's motion is to examine whether motion blurring occurs. The motion blurring indicates a phenomenon that a moving past remains in a taken image when a moving object is taken through an image input device whose shutter speed is low. Examination on the motion blurring was conducted by normalizing an image for a certain area of a horizontal edge part of the common pupil. The image which passes through the resolution examination and the noise examination provides a high image quality for iris recognition, and this procedure was an essential one for increasing a recognition rate.
However, the prior method for obtaining the good image among the plurality of the images taken from the image input device has different threshold values according to colors of the pupils and each human race. Accordingly, it can be hardly applied to nations where various ethnic groups are mixed together. Also, since the features of the irises between Westerners and the Oriental people are different when threshold values are used in the resolution examination, it has a problem that the same threshold values cannot be applied.